Streptococcus disease is one of the most serious and difficult diseases in tilapia aquaculture. It is highly contagious and has a mortality rate of over 80%. Recently, farmers have reported that Streptococcus tilapia has come again.
Streptococcus is a Gram-positive bacteria, usually mainly in the sediment, spread with water, especially in eutrophic conditions of water can survive for a long time. Once it enters the high temperature period (above 30°C), it begins to explode with the great changes in the water environment. Weak fish will be infected first, and then continue to infect sub-healthy fish in the pond, eventually leading to a large number of dead fish in a short period of time, which cannot be stopped! It can be said that once the tilapia is infected with streptococcosis, it is similar to having a "terminal illness", and the "terminal illness" will continue to spread.
 
Symptoms
Acute type of infection: neurological symptoms are the main manifestations, and the diseased fish rotates and swims in arcuate bending.
Chronic infection: The diseased fish has symptoms such as eyeball, gill, pectoral fin, hepatic portal congestion, and exophthalmos.
After autopsy, it can be seen: hepatobiliary enlargement, bile leakage, jejunum empty stomach, hydrops in part of intestinal tract, liver congestion, spleen color deepening, etc.
Note: Once the above symptoms appear, qualified farmers can do tissue section staining to confirm whether it is streptococcal infection.
Origin and Transmission of Streptococcus
 
Sources: 1. Self-contained seedlings; 2. Residual sediments; 3. Water pollution.
Transmission medium: diseased fish feces, corpses, etc. spread with water very quickly. Especially when the water temperature is above 30 ℃, it can spread throughout the whole pool within a week.
Pathogenesis: After Streptococcus enters the fish, it directly invades the cells and produces toxins, which in turn destroy the cells, affect the normal metabolism of the fish, and eventually lead to death.
Water temperature, physique and pond environment are the three elements of streptococcal outbreak. Be fully prepared before entering the high temperature period. By means of water adjustment, bottom improvement, and regular disinfection, the water environment is strictly controlled, the reproduction of streptococcus is inhibited, and the transmission route of streptococcus is cut off. Because once suffering from streptococcus, the cost of treatment is high, and the mortality rate is relatively high. Streptococcus has the characteristics of rapid infection, rapid onset, and high mortality. It is no exaggeration to call it "the number one killer of tilapia".
 
Therefore, in the breeding process of streptococcus, it is recommended to give priority to prevention. In addition to providing a good living environment, it is also necessary to strengthen immunity and enhance physical fitness. The teacher has seen that some farmers will mix antibiotics and feed them together during prevention. Long-term feeding of antibiotics will cause drug resistance. The preventive health care teacher recommends the use of Chinese herbal medicine prevention and control products, which not only provide comprehensive protection, but also do not damage the health of tilapia, do not affect feeding and growth, and have no drug residues and drug resistance. . Farming "prevention first, combined with prevention and treatment" is not an empty slogan, it needs to be done, prevention is not random use of drugs, and antibiotics should not be used for a long time.